Co in the periodic table of elements is cobalt. Located in group nine, period four of the periodic table, this transition metal has an atomic number of 27 and an atomic weight of 58.9. It is a hard element that appears bluish-gray in color.

George Brandt, a Swedish chemist, was the first person known to isolate this element in the 1730s. Cobalt is found in various minerals and in meteorites. Salts from this element are used to give a brilliant blue color to glass, tiles and pottery. Cobalt forms alloys with iron and other elements. An isotope of this element is also used in sterilization processes and in radiation therapy.